Dual motion surface-dressing machine



Dem 1970 w. H. SCOTT ETAL DUAL MOTION SURFACE-DRESSING MACHINE OriginaIl-iled Jan. 11, 1965 3' Sheets-Sheet. l

zuvzu'rons WILLIAM u. soon EARL I. SHIT" ATTORNEYS ,1970 w. H. sco'r'r ETAL 3,543,449

DUAL MOTION SURFACE-DRESSING MACHINE Original Filed Jan. 11, 1965 3 Sheets-Sheet 2 ll Illlllllfifll vIII III IIII IiIiI'II' ATTORNEYS Dec. 1, 1970 w. H. sco'r'r ETAL 3,543,449

DUAL MOTION SURFACE-DRESSING MACHINE Original Filed Jan. 11, 1965 KSheets-Sheet 5 ll W1,; mwwmmm INVENTORS WILLIAM H. SCOTT EARL E. SMITH y di W 1 ATTORNEYS 3,543,449 DUAL MOTION SURFACE-DRESSING MACHINE William H. Scott, Glen Ellyn, and Earl F. Smith, Lombard, Ill., assignors to G. W. Murphy Industries, Inc., a corporation of Texas Original application Jan. 11, 1965, Ser. No. 424,715, now Patent No. 3,375,616. Divided and this application Nov. 28, 1967, Ser. No. 686,065

Int. Cl. B24b 23/00 U.S. Cl. S1170 3 Claims ABSTRACT OF THE DISCLOSURE A surface-dressing machine is provided which has an externally actuated member for converting the motion of the surface-dressing member from reciprocating motion to orbital motion. The machine also has externally actuated members for locking or unlocking the sand paper or the like to the machine. The housing is designed in relation to the surface-dressing platen that suction inside the housing will draw dust into and through the housing. A means is provided between the driving means and the surface-dressing platen for reducing the ill-effects of misalignment of the drive pin therebetween. A novel mechanism is provided for converting the rotary motion of the driving means to either reciprocating motion or orbital motion of the surface-dressing member.

This application is a divisional application of applicants co-pending application Ser. No. 424,715, filed Jan. 11, 1965, Pat. No. 3,375,616 assigned to the assignee of the present application.

This invention relates to power operated surface-dressing machines and more specifically to an improved dual motion surface-dressing machine.

Currently surface-dressing machines are generally capable of performing either only reciprocating motion of the surfacing plate or only orbital motion of said plate. One such machine is capable of performing both motions, but the change from one motion to another necessitates stopping the machine and inserting a special tool to effeet a changed mechanical relation, such for instance that reciprocating motion can be changed to orbital motion or the reverse. This system of conversion from one motion to another is inefficient, is time-consuming and is somewhat expensive, i.e., requiring special tools.

In addition, to make current surface-dressing tools operate substantially dust free requires the positioning of a special vacuum shroud over the machine, which shroud stands away from the machine making it impossible to effectively work flush with corners, walls or other obstructions. The shrouds, being essentially of a stiff material, vibrate in such a way that dust and other foreign matter on the work surfaces are agitated and stirred up ahead of the tool, making the attempt to reduce the dust ineffective.

Presently available surface-dressing machines also have complex means for effecting the insertion of the strips of abrasive material into the housing for locking in position on the plate. These relatively complex means do not provide any method for guiding the strip of material into a position to be clamped and as a result the ends of the strip of material often curl, bend and crack, becoming almost impossible to line up in position to be clamped to the plate.

It is, therefore, a principal object of this invention to overcome the above noted disadvantages of the prior art and to provide a surface-dressing machine having improved features throughout.

nited States Patent It is also a principal object of this invention to provide an improved surface-dressing machine having selectively available diiferent motion patterns for the surface-dressing member.

It is another principal object of this invention to provide an improved surface-dressing machine having a self contained dust removing feature.

It is still another principal object of this invention to provide a surface-dressing machine having an improved sheet material inserting and retaining mechanism.

And it is still another important object of this invention to provide a sheet material backing member that will not deteriorate or disintegrate with moisture.

Still another object of this invention is to provide an improved mounting principle for the surface-dressing member which will permit flush sanding into corners and other close surface discontinuities.

A further object of this invention is to provide an improved surface-dressing mechanism wherein surfacedressing motion patterns can be changed while the surface-dressing mechanism is in operation.

A still further object of this invention is to provide an improved bearing mounting wherein discrepancies from the normal angular relationship between the plane of the surface-dressing member and the axis of the driving shaft lying perpendicular to the plane of said member can be tolerated.

Another object of this invention is to provide an improved balancing of the forces between the driving portion of the mechanism and the surface-dressing member for better operation of the machine.

And another object of this invention is to provide an improved means for guiding the end of a strip of material into position to be clamped to the base plate assembly.

And still another object of the invention is to provide an improved housing mounted device for locking the sheet material clamping member in the open position for more efficient reception and removal of the sheet material.

These and other objects, features and advantages of the invention will be apparent from the following detailed description taken in connection with the accompanying drawings, in which:

FIG. 1 is a side elevational view of the improved surface-dressing machine;

FIG. 2 is a partial rear elevational view of the surfacedressing machine of FIG. 1;

FIG. 3 is a sectional view taken along line 33 of FIG. 2;

FIG. 4 is a sectional view taken on a plane along the longitudinal centerline of the surface-dressing machine and showing some parts in full;

FIG. 5 is a sectional view taken along lines 55 of FIG. 4;

FIG. 6 is a partial view in section similar to the righthand portion of FIG. 4 but with parts in another operative position;

FIG. 7 is a sectional view taken along the lines 77 of FIG. 4;

FIG. 8 is a sectional view similar to FIG. 7 but with the parts in a different operative position;

FIG. 9 is a sectional view taken along the line 99 of FIG. 1;

FIG. 10 is a sectional view taken along the lines 1010 of FIG. 6; and

FIG. 11 is a sectional view taken along the line 77 of FIG. 4 looking in the opposite direction of the arrows.

As shown in the drawings for purposes of disclosure, the invention is illustrated and embodied in a dual motion surface-dressing machine having a housing with a motor for driving a surface-dressing member. A means is provided for giving the surface-dressing member either a reciprocating motion or an orbital motion. A motion selecting means is mounted on the outside of the housing which can be operated between two positions; in one position the surface-dressing member is driven with an orbital motion and in another position the surface-dressing member is driven with a reciprocating motion.

A sheet of abrasive material can be attached to the surface-dressing member by a novel guiding means and clamping means. The clamping means is mounted on the top surface of the surface-dressing member and the strip of material to the surface-dressing member. The guiding means is carried by the top surface of the surface-dressing member in coacting relationship with the clamping means such that releasing the clamp means permits the guiding means to move into a position to guide the end of a strip of material into position to be clamped to the surfacedressing member. The surface-dressing member has a novel resilient pad which is adapted to be molded or shaped for use with a backing member of the surfacedressing machine and is of such a nature that moisture will not deteriorate the pad. The pad presents a surface with a high coefiicient of friction to the back of the sheet of abrasive material which holds the sheet against creeping relative to the pad.

Mounted on the housing for actuation from outside the housing is a clamp release means which is adapted to engage with and release the clamping means upon inward movement of said clamp release means. The clamp release means includes means for holding the clamping means in 21 released position.

To keep the work surface free of dust and other airborne foreign matter, a self contained system is provided which includes a novel relationship between the edge portions of the surface-dressing member and the edge portions of the housing such that when a pressure differential is provided between the inside of the housing and the surface surrounding the edges of the surface dressing member, air will be drawn into the housing close to the work surface in such a way as to bring dust and other airborne foreign particles into the housing for disposal.

Referring now to the drawings wherein similar reference numerals will refer to similar parts throughout the several views, a dual motion surface dressing-machine or sander is shown having a housing or body 21 to which is integrally formed a handle 22 outwardly extending from one side thereof and a hollow inverted rectangularly shaped bottom portion 23 formed on the lower part of said body. A knob 26 may be screwed into any one of three treaded openings 24 provided in the three walls of the housing that do not support the handle 22. For certain types of sanding jobs it becomes necessary or important to use both hands, one on the handle 22 and the other on the knob 26. In this way, the sander can be turned or pressure applied in any desired direction. The ability to position the knob 26 in any one of three locations adds to the flexibility of the tool.

The handle 22 has a plug 25 secured therein by means of protruding lugs 26 on the casing 27 being gripped between the two mating side halves 28, 28' of the handle. A wire 29 extends from the plug 25 to a switch actuated by an on-off trigger 30 mounted on the handle 22, the wire then continues from the switch to the motor, not shown, mounted in the housing or body 21. The plug 25 has a bayonet slot 31 formed in the wall of the casing 27 for receiving a coacting lug 26' on the side of a mating plug 25' carried by an extension cord 27'. A plurality of prongs 29' are electrically connected with the wire 29 through an insulated base 30' within the casing 27. A spring 31 acts against the one end of the casing 27 and against the insulated base 30 for urging the outwardly extending lugs 32' on the sides of the base 30" against the forward ends of slots 33' formed in the rearward portions of the wall of the casing 27. The mating plug 25' has recesses for receiving the prongs 29 on the plug 25 when the lug 26 on said plug 25 is aligned with and moved in the bayonet slot 31 in the casing 27 against the urging of the spring 31'. The spring 31' is depressed as the mating plug 25' is inserted until the lug 26' can be turned and seated in the locking portion 34" of the bayonet slot 31 whereupon an electrical connection is established to the switch on the tool.

With this construction of the plug 25 it is possible to provide one extension cord 27 for many different hand tools, such as drills, saws, different types of sanders and the like. Instead of the inconvenience of several cords that must be wrapped around the tools for storage and often create problems of shorting at the junction of the cord with the tool due to continuous flexing in use and storage, the new connection makes it possible to more easily store the tools; shorts created by the flexing at the junction of the tools are eliminated and the number of cords required for two or more tools is reduced to a minimum.

Inasmuch as it is one of the objects of this invention to provide a surface-dressing machine with an output means mounted relative to the housing of the machine in a manner that permits surface-dressing or sanding flush into corners and other surface discontinuities, a novel relationship is provided between overlapping edges of the housing and of the surface-dressing member making it possible to reduce to a minimum the spacing between said edges so that the movement of the surface-dressing member will not interfere with the housing and yet said surface-dressing member will sand flush into corners. The minium spacing of the edges also contributes to another important feature of the invention which will be referred to hereinafter. The surface-dressing member or rectangularly shaped base plate assembly 32 is resiliently supported within and in slightly overlapping relationship to the opening 33 defined by the edges 34 of the hollow inverted bottom portion 23 of the housing by means of four elongate resilient legs or supports 35. Each leg or support 35 has a tapered round body 37 made of rubber or similar resilient material which at one end is molded around or secured to a stepped ferrule 38 internally threaded at 39 and at the other end is secured to a ferrule 40 having a stepped down body 42 forming a shoulder 43 with a transverse aperture 44 passing through said body 42. A screw 45 passes through an aperture 47 in a back plate 48 of said surface-dressing member or base plate assembly 32 and into the threaded aperture 39 of the leg or support 35 for securing the base plate assembly 32 to the supports 35.

As shown in FIG. 5, one side wall of the bottom portion 23 of the body or housing 21 has a recess 49 into which is inserted an elongated screw 50 passing through the apertures 44 in the supports 35 which supports are held spaced apart by a sleeve 52 encircling the screw 50. The screw 50 has threads 53 thereon threaded into a lug 54 in the opposite side wall of the bottom portion 23. A pair of screws 50, as shown in FIG. 4, are used to secure the four legs or supports 35 to the housing 21. Therefore, the surface-dressing member or base plate assembly 32 is resiliently connected to the housing through the four legs or supports 35.

The base plate assembly 32 has the back plate 48 formed of sheet material of substantially rigid construction with a peripheral edge portion 55 extending completely around the back plate and being angularly disposed downwardly and outwardly with respect to the main body portion 57 thereof. A pad 58 formed of hard rubber or polyisoprene is bonded or attached as by gluing to the back plate 48 and has a peripheral portion 59 with a downwardly and outwardly tapered top surface angularly disposed with respect to the main body portion '59 of said pad 58. The angled surface of the peripheral edge portion 59 of the pad lies at substantially the same angle as the edge portion 55 of the back plate 48 so that a substantially uniform angularly disposed edge portion is formed about the outer periphery of the surface-dressing member or base plate assembly 32. The pad 58 is made of a material such as hard rubber that can be molded to shape with the tapered top surface on the edge portion 59. The material from which the pad is made has a high coefficient of friction which coacts with the back surface of a sheet of adbrasive material 60 to resist creeping of the material relative to the pad. In this way the sheet of material does not became loose on the pad and every motion of the pad will be motion of the abrasive sheet relative to the surface being treated.

In order to affix the strip of material or a sheet of sandpaper 60 to the base plate, novel means is provided which not only serves to guide the end of the strip or paper into a proper position, but also cooperates with a clamping means to grip and secure the strip or paper in a locked position for use. This clamping means comprises a pair of identical space apart clamp members 62 mounted on the back plate 48 at oppositely disposed end portions 63, 64 of said baseplate assembly 32. Each clamp member 62 has a body portion 65 with an upwardly disposed actuator arm 67 and a downwardly disposed gripping portion 68. A pair of mounting tabs 69 extend downwardly from said body portion 65 and are pivotally engaged by a pin 70 extending parallel to the back plate 48 through upwardly disposed mounting lugs 72 attached to said back plate 48. A spring 73 is wrapped around said pin 70 with one end 74 engaging with the back plate 48 and with the other end 75 engaging with the back of said actuator arm 67 for urging the gripping portion 68 of said clamp member into engagement with said back plate.

Attached at one end 76 to the back plate 48 substantially midway between each pair of laterally spaced legs or supports 35 is a guide member 77 having an elongate body portion 78 and an integrally formed angularly disposed end portion 79 lying, in one position, against the back of said back plate 48 and substantially conforming to the contour of said back plate. The guide member 77 is made of resilient material such as sheet spring steel and is formed in such a way as to urge the free end portion 79 into a position away from said back plate 48 as is shown in FIG. 6. The force of the spring 73 on the clamp member 62 is stronger than the resilience of the said guide member 77 such that the force of spring 73 urges the clamp means against the body portion 78 of the guide member 77 for flattening said guide member 77 against the back of said back plate. The gripping portion 68 of the clamp means 62 has a pair of spaced apart prongs or points 80 projecting downwardly therefrom and being adapted to align with and extend through the apertures 82 in the body portion 78 of the guide member 77 and the apertures 83 in the back plate 48.

In order to actuate the clamp means and guide means without removing the base plate from the housing or without the use of some other special tools, a release means is provided on the housing 21 which is actuated from outside the housing and which is positioned relative to the clamp means in such a way that the clamp means will be moved out of clamping position and the guide means will move into guiding position relative to the housing. The release means has a locking feature which acts to hold the release means and the clamp .means in released position so that the strip of abrasive material or sheet of sandpaper can be inserted or removed from the base plate with ease. A separate release means is provided for each clamp means and each release means comprises a release member 85 having a body portion 87 slidably disposed in an aperture 84 in the end wall 86 of the bottom portion 23 of the housing. The release member 85 also has an eX- ternally extending actuator portion 88 and a contact portion 89 disposed in the housing in close proximity to the actuating arm 67 of the clamp 62. Suflicient clearance must be provided between the contact portion 89 and the actuating arm 67 to permit the base plate assembly to which the clamp member 62 is attached to move freely and without interference through the orbital or reciprocatory motions required of the machine. A rib 90 is formed on said body portion 87 and is adapted to slide between the spaced ledges 92 carried by the walls of the housing for guiding the movement of the release member 85. An offset or stop 93, spaced inwardly from the wall 86, is formed in the ledges 92 in said housing in a position to be engaged by the front corner or edge 94 of the body portion 87 of said release member 85. A compression spring 95 has one end encircling a lug 97 on the back portion of the release member 85 and has the other end connected to the sleeve 52 around the elongated pin or screw 50.

The spring 95 urges the release member 85 into the inactive position of FIG. 4 with the surface 98 of the contact portion 89 engaging with the edge 99 of the ledges 92. An operator pressing inwardly against the releasing member 85 compresses the spring 95 and engages the contact portion 87 with the actuating arm 67 of the clamp 62 to pivot the clamp about the pin 70 so as to release the gripping portion 68 from the guide member 77 and from the plate 48. The front corner 94 on the release member 85 will engage with the stop 93 on the housing to hold the clamp in the released position.

As the clamp member 62 is pivoted, the gripping portion 68 will move upwardly whereupon the free end portion 79 of the guide 77 will also move upwardly away from the back plate 48 and from its edge portion 55 until said free end portion 79 comes into contact with the edge 34 of the housing 23. In this position the guide 77 forms an open ended slot into which the end of a strip of material 60 can be easily inserted. The guide 77 and the back plate 48 being relatively smooth permits ready ingress of the strip of material 60 without interference into a position between the guide 77 and back plate 48 such that movement of the clamp member into engagement with the guide 77 will clamp the strip of material 60 to the base plate assembly.

With the releasing member 85 locked in the clamp member released position of FIG. 6, an upward movement of the actuating portion 88 of the releasing member 85 will disengage the front corner 94 from the stop 92 permitting the spring 95 to drive the releasing member 85 into an inactive position with the surface 98 of the contacting portion 89 in engagement with the ledges 92. The spring 73 on the clamp 62 will force the prongs 80 on the gripping portion 68 through the apertures 82 in the guide member 77 and will depress the guide member against the end portion of a strip of material and against the back plate 48 for clamping the material in position on the base plate assembly. The prongs 80 will bite into the strip of material as they pass through the aligned apertures 82 and 83 in the guide and back plate, respectively, providing a further positive locking action for the strip of material to the base plate assembly.

The surface-dressing machine has a motor which is connected with the surface-dressing member or base plate assembly in such a way as to provide the surface-dressing member or base plate assembly with either reciprocating motion or orbital motion depending upon the selection made by the operator. The change from one motion to the other can be accomplished with means provided on the outside of the housing. The motion changing means can be activated while the surface-dressing member or base plate assembly is in motion and is interconnected with parts of the connection between the motor and the base plate assembly by a novel means for effecting the change. An improved system for balancing the forces in the driving means for the surface-dressing member or base plate assembly is provided which produces a better operating surface dressing machine.

Within the housing '21 is mounted a conventional motor (not shown) having a vertically disposed shaft 102 mounted in a bearing 103 and having a set of gear teeth 104 formed in the lower end portion thereof. A stub shaft 105 is mounted by means of bearings 107, 108 in said housing and has fixed thereon a pinion gear 109 meshing with said gear teeth 104 on the shaft 102. The bearing 108' has a sleeve 110 with inturned ends 111 for retaining a multiplicity of elongate cylindrical bearing pins 112 which are adapted to roll about a longitudinal axis which is parallel to the longitudinal axis of the shaft 105. This type of bearing 108 has particularly good characteristics for maintaining a predetermined alignment of a rotating shaft supported by said bearing.

The bearings 103, 107 and 108 are nested in appropriate cavities in the housing 21 which together with the motor shaft end 104, pinion 109 and shaft 105, are enclosed by cover plate 114 screwed into place by screws 113. Fixed on the lower part of the shaft 105 to rotate therewith is a weighted disc member 117 which is rotatable in a plane perpendicular to the axis 105 of the shaft 105. The disc member 117 is circular in shape and has an insert 116 keyed in an aperture 119 offset from the true center 115 of the disc member 117 and located on a radius between the true center of the disc member 117 and one peripheral edge portion thereof. The shaft 105 is connected to the insert 116 of the disc member with the axis of the insert coinciding with the axis of the shaft 105 so that rotation of the shaft 105 rotates the disc member 117 about the common axis 105' of both the shaft 105 and the insert 116. The disc member 117 will be rotating as an eccentric and will create a counter-weight effect with the center of the counterweight mass acting at a point called the center of gravity 117' located on the diameter of the disc member passing through the true center 115 of the disc member and the axis of rotation of the insert 116.

A driving pin 118 is fixed to the insert 116 of the disc member 117 and extends downwardly therefrom with the longitudinal axis of the pin 118 offset from the longitudinal axis of rotation of the insert 116. The longitudinal axis of the pin 118 lies on the common diameter of the disc member which diameter passes through the true center 115 of the disc member, the axis 105 of the insert 116 (or axis of rotation of the disc) and the center of gravity or the point 117' at which the counterweight mass effectively acts. The just enumerated location of the pin 118 creates an imbalance in the disc member which is balanced by the location of the center of the mass of the counterweight on the opposite side of the axis of rotation of the disc member. The counterweight mass provides an excess of counterbalancing forces over what is needed for counterbalancing the weight of the pin which will be described more fully hereinafter. In addition, the excess of weight of the disc member 117 produces to some extent a flywheel effect for the drive pin 11 and as such produces extra forces for keeping the mechanism operating once it has been started in motiton.

Rotation of the shaft 105 by the motor will rotate the disc member 117 about the axis 105 of the insert 116 of the disc member with the pin 118 subscribing a circle about the axis of the shaft, which motion of the pin 118 is described as orbital motion.

Substantially centrally disposed longitudinally and laterally of the base plate assembly and connected to the back plate 48 is a channel shaped track member 120 opening upwardly away from said plate assembly and having an axis parallel to the sides 121 of the channel, which axis is disposed a few degrees off the axis lying transverse to the longitudinal axis of the base plate assembly. The few degrees deviation from the true transverse axis has been arrived at by experience wherein it has been found that the reciprocatory motion of the base plate assembly 32 will be along the longitudinal axis of the housing if the connecting means is skewed slightly from the transverse axis.

The channel or track has an enlarged part 125 of a lever 126 pivotally mounted centrally of said track by means of a hollow rivet 127 passing through the part 125 of the lever, the track 120 and the back plate 48 of the base plate assembly. A slight cavity 128 is formed in the pad 58 so that a turned over end 129 of the rivet 127 will not bulge the pad downwardly. The part 125 of the lever 126 has a struck down portion 130 around the aperture 132 which struck down portion 130 serves as a bearing and as a support for the rivet 127 as it extends through the openings 133, 134, respectively, in the channel or track 120 and the back plate 48. A collar 136 is formed on the upper part of the rivet 127 for holding the lever and channel assembled on the back plate 48. The channel or track 120 is rigidly attached to the back plate against movement relative thereto by means of welding or any other appropriate attaching means.

A block 138 is shaped to fit into and slide relative to the channel or track 120 and has a recess 139 in the top surface into which is seated an antifriction ball-type bearing 140. The outer race 142 of the bearing is cushioned from the wall 143 of recess 139 by a sleeve formed of a thin layer of rubber or other resilient material 144 which can be press fit between said race 142 and said wall 143 or bonded to asid race 142 and to said wall 143 in any well known fashion. The pin 118 on the disc memher 117 extends into the inner race 146 of the bearing 140 whereby the orbital movement of the drive pin 118 is transmitted to the block 138. A compression spring 147 surrounds the pin 118 between the disc member 117 and the inner race 146 of the bearing 140 to urge the block into nesting relatiton within the channel or track 120.

The sleeve 144 being positioned between the surface dressing member or base plate assembly and the pin 118 of the driving means permits slight skewing or misalignment between the plane of the surface dressing member or base plate assembly and the axis of the pin 118 lying perpendicular to said plane which helps reduce the side load on the bearings of the shaft 105, adding to the life of the whole machine. The sleeve 144 also absorbs a small amount of the shock effect caused by the surface dressing member or base plate assembly encountering an unexpected obstruction that might under certain conditions have stalled or sparked the motor. The sleeve 144, therefore, is an important feature contributing to the improved operation of the sander.

Earlier in this description, reference was made to an excess of balancing forces created by the counterweight mass of the disc member 117 over the weight necessary to balance the weight of the drive pin 118. Since the block 138 travels with the pin 118 when the lever 126 is in either of the two positions which creates one or the other of the two motions of the surface dressing member, it is considered to be part of the pin 118 so that the weight of the block 138 and the weight of pin 118 added together are considered to be acting at a radius equal to the radius of the circle generated by the pin 118 rotating around the axis of the shaft 105. The weight of the disc 117 acting at the center of gravity 117' of the disc is considered to be acting at a radius extending between the axis 105 of rotation of the disc 117 and the center of gravity 117. The centrifugal forces created by the weight of the disc 117 acting through the center of gravity of the disc is used to substantially balance the centrifugal forces created by the sum of the weights of the pin 118 and block 138 acting at the radius of rotation of the pin 118 about the axis 105' on the side of the axis 105 opposite to the side bearing the center of gravity of the disc. The illustratiton of the center of gravity of the disc 117 as being at point 117 is exemplary only. The center of gravity can be varied along the diameter of the disc passing through the center of rotation 105' and the true center of the disc 115 to any point desired depending on the results of the computations of forces needed to balance a particular force carried on the pin 118.

During the orbital motion of the surface dressing member, the block 138 is locked to the channel and to the surface dressing member such that the weights of those elements are added to the Weights of the block and pin to create the forces on the one side of the center of rotation 105' of the disc. During reciprocating motion of the surface dressing member the forces are considered to be both rotating and reciprocating and as such cannot be completely balanced. Since it is not possible to completely balance the forces of the system for both reciprocating motion and for orbital motion, it has been concluded to compromise such that the weight of the disc acting through the center of gravity of the disc balances in large measure the extremes of forces of the surface dressing member, channel, block and pin during both orbital and reciprocating motions. Actually there is an excess of weight on the surface dressing member side of the balance, which weight acts as a form of flywheel which contributes added forces to the abrasive surface being moved over a work surface. This flywheel effect improves the effective power given to the abrasive surface which results in more sanding, abrading or polishing by the machine.

The motion selection means comprises the lever 126 with the enlarged part 125 having a pair of substantially parallel surfaces 148, 149 diagonally offset on opposite sides of the pivot axis of the rivet 127. The surfaces 148, 149 are substantially planar throughout the length thereof and at each end curve slightly about the corners 175 forming obtuse angles with other non-functional edge surfaces of the lever. The parallel planes of the surfaces 148, 149 are intersected by the longitudinal axis of the lever arm 152 at acute included angles. The lever arm 152 has an end portion 153 extending outwardly into position to be contacted by one or the other of two abutments 154 projecting from the body 155 of a slide member 157 carried in an elongated slot 158 in the wall of the hollow portion 23 of the housing 21. The two abutments 154 on the slide member 157 are spaced apart from each other and from the end portion 153 of the lever arm 152 a distance at least great enough to permit the movement of the lever 126 created by the orbiting or reciprocating of the surface dressing member or base plate assembly attached to said lever 126 without movement of the slide member 157. The connection between the slide 157 and the lever 126 is sometimes referred to as a lost motion connection. The slide 157 is held in sliding position on the housing by means of a clip 156 fastened by means of a screw 159 to the housing and having an overlapping arm 160 engaging the body of the slide to permit the slide 157 to traverse the slot 158 from one extreme to the other. A raised outwardly extending grip portion 161 on the body 155 is adapted to be engaged for urging the slide one way or the other within the slot 158. A scissors type spring 163 having one end seated in an opening 164 in the back plate 48 and having another end seated in an opening 165 in the outer end portion 153 of the lever urges the lever 126 into one position against a stop 167 on the back plate 48 for reciprocating or straight line sanding or into another position remote therefrom for orbital sanding.

The block 138 is formed of relatively heavy material as for example iron-nickel powdered metal, oil impregnated for lubricating purposes. The iron-nickel powdered metal forms a block of high density material creating a concentrated mass which can be used to supplement or balance the forces for the various motions contemplated by the machine. The lower portion of the block 138 has a hollowed out portion consisting of a pair of walls 169, 170 contiguous with the sides of the block and extending downwardly from a planar center surface 171 within the hollowed out portion of the block. The inner surface of the wall 169 within the hollowed out portion has a planar portion 172 parallel to the outer surface of the wall 169 of the block, an angled recessed portion 173 and another planar portion 174 parallel to the outer surface of the wall 169 but spaced therefrom a distance greater than the spacing between the first planar portion 172 and the outer surface of the wall 169. The wall 170 has the same inner surface configuration but reversed end for end; that is, for instance, the surface 174 on wall 169 is opposite to surface 172 on the wall 170. The angled recessed portions 173 lie in planes substantially parallel to each other and intersect the longitudinal axis of the block at acute included angles. The acute included angles between the planes of the surfaces of the recesses 173 and the axis of the block substantially equal the acute included angles between the planes of the surfaces 148, 149 of the lever 126 and the axis of the lever arm 152. The length of the surfaces 148, 149 on the lever 126 is substantially equal to the length of the surfaces of the recesses 173 such that in one position of the lever 126 the surfaces 148, 149 are seated in the recesses 173 so as to lock the block 138 to the channel or track and to the surface dressing member or base plate assembly 32 as is best shown in FIG. 7.

With the surfaces 148, 149 of the lever arm 126 seated in the recesses 173 of the hollowed out portion of the block 138, the orbital motion of the drive pin 118 is transmitted directly to the block 138, channel 120 and base plate assembly 32 so that orbital movement of the surface dressing member relative to the housing results.

Movement of the slide 157 engages abutment 154 with the end 153 of lever 126 to pivot the level 126 to remove the surfaces 148, 149 from the recesses 173 in the hollowed out portion of the block, as shown in FIG. 8, whereupon the block can now reciprocate relative to the channel or track 120. The corners 175 on the diametrically opposite surfaces 148, 149 protrude into the recesses 173 and provide limits for the movement of the block relative to the channel by said corners contacting intermediate portions of the surfaces 173 of the recesses. However, these limits are never reached in practice because the extent of movement transmitted to the block by the pin 118 is less than the distance between the extremes of movement of the block.

With the block 120 able to reciprocate relative to the channel or track 138, the orbital motion of the pin 118 will impart only a longitudinal component of motion to the channel 120 and to the surface dressing member or base plate assembly 32 to produce in efiiect straight line longitudinal motion in the surface-dressing member. The block sliding in the channel or track 120 along the axis of the channel will give no component of movement to the surface-dressing member or base plate assembly 32 in the direction transverse to the longitudinal axis of the housing.

It can be readily seen, therefore, that movement of the slide 157 from one position to another will change the motion of the surface-dressing member or base plate assembly 32 from reciprocating motion to orbital motion or back again without stopping the motor and without the need for special tools or fixtures.

With the motion selection means positioned with the arm 152 of the lever 126 bearing against the stop 167 as shown in FIG. 8, the surfaces 148, 149 will be out of engagement with the recesses 173 and the block 138 will transmit reciprocating motion to the surface dressing member along the longitudinal axis of the housing. To now change the type of motion of the surface-dressing member to orbital motion, the actuator 157 is moved to the right to pivot the lever 126 in a counterclockwise direction. The corners 175 on the opposite ends of the planar surfaces 148, 149 on the enlarged portion of the lever 126 engage with the surface of the recesses 173 in the hollowed out portion of the block and slides the block a short distance relative to the channel or track 120 toward the actuator 157 until the surfaces 148, 149

align with and nest in the recesses 173 in the block 138 as the lever 126 is resiliently urged into that position by the spring 163. The spring 163 urges the enlarged portion 125 of the lever into the nested position of FIG. 7 and due to the way the spring 163 is anchored to the back plate of the surface-dressing member, the urging action of the spring is attempting to rotate the coacting block 138 in the channel or track 120 about the axis of the rivet 127 which further acts to lock the block to the channel and accordingly to the surface-dressing member. The orbital motion of the pin 118 is now transmitted directly to the block, channel and surface-dressing member to provide orbital motion to said surface-dressing member relative to the housing.

From the above, it can be readily seen that movement of the actuator in either direction will be possible even with the surface-dressing mechanism in operation. The surfaces 148, 149 on the lever 126 being locked to the surfaces of the recesses 173 for orbital movement of the surface-dressing member and being free of the surfaces of the recesses 173 for reciprocating movement of the surface-dressing member with the corners 175 of the ends of the surfaces 148, 149 of the lever acting as camming surfaces to make contact with portions of the recesses 173 to move the block 138 relative thereto until proper nesting between the portion 125 on the lever 126 can take place with the hollowed out portion of the block.

As stated hereinbefore the surface-dressing member or base plate assembly 32 is positioned partially within the open side of the bottom portion 23 of the housing 21 so as to permit flush sanding with the machine; it was also indicated that the positioning of the base plate at a minimal distance from the edge of the housing had another purpose, namely, to provide a restricted passage 4 through which air could be driven into the housing, bringing dust and other loose foreign particles along with it. A vacuum source is connected through an opening directly into the hollow base of the housing such that drawing air from the housing through said opening will draw the air and dust into the housing through the minimal opening around the edge of the plate. Drawing the air into the housing around the edge of the base plate, being close to the work surface, and being angled upwardly therefrom will provide a maximum of surface and air cleaning at the point of maximum air and surface contamination, thereby producing the best cleaning results. Accordingly, the hollow bottom portion 23 of the sander or surface-dressing mechanism has an aperture 180 through one end wall 86 into which aperture is fitted a collar 181 having an outwardly tapered wall portion 182 therein. A source of vacuum can be connected to the housing through a hose, not shown, having a tapered nozzle on one end which is adapted to be wedged into the tapered portion 182 of the collar 181 in the housing 23. Around the bottom edge 34 of the hollow portion 23 of the housing 21 is attached a resilient bumper 185 which has a tapered edge portion 186 facing inwardly of the housing. The tapered edge of the bumper completely encircles the periphery of the housing and conforms to some extent to the taper on the outer peripheral edge portions 55, 79 of the base plate assembly and guide member 77, respectively. The base plate assembly 32 is positioned in the opening 33 in the housing in an overlapping relationship with respect to said tapered bumper 185. The spacing between contiguous peripheral edge portions 55 of the base plate 32 and the tapered portion 186 of the bumper 185 is as small as it can be made without interference between the surface-dressing member or base plate assembly 32 and herein this is accomplished by the bevel on the surface-dressing member and the corresponding bevel on the housing with the centerline of the opening therebetween forming an angle of approximately 45 so as to permit movement of the surface-dressing member a distance greater than the transverse distance between the two overlapping surfaces when the surface-dressing member is at normal or rest position. With the angle of the centerline between the two overlapping surfaces of the housing and surface-dressing member varying from a few degrees up to a few degrees from the position, the horizontal distance between the surfaces will be greater than the horizontal travel of the surface-dressing member relative to the housing. The opening between the beveled surfaces can be smaller than would be required if the surfaces were at right angles to each other such that an opening, being the result of the angled relationship between the beveled surfaces, does not limit the relative movement of the overlapping surfaces. With the angularly disposed, overlapping beveled surfaces, it is possible to have a smaller opening therebetween for the same horizontal movement of the surface-dressing member. The angled overlapping surfaces between the housing and dressing member also results in a minimum opening variation during operation of the mechanism. The minimum opening variation is important in producing a surface-dressing mechansm which has an efi'icent and effective amplitude of motion for the surface-dressing member while at the same time keeping the opening between said member and the overlapping housing to a minimum so that a more efiicient air flow into the housing will be created when a differential in pressure between the inside and the outside of the housing is produced.

When a pressure differential is created between the hollow bottom portion 23 of the housing by a suction outwardly through the aperture 180, the relatively small spacing between the tapered portion 186 of the bumper and the tapered portion 55 of the surface-dressing member or assembly 32 will make it possible for a relatively large volume of air to be drawn therethrough at high velocity, bringing with it loose dust and other stray particles of contamination lying or floating in and around the vicinity of the surface being treated by the surfacedressing member.

The tapering of the edge portions 55 of the base plate assembly 32 permits the edges of the pad to extend outwardly of the opening in the housing to an extent that makes it possible for the edges of the surface-dressing member or base plate assembly, when reciprocating or orbiting, to reach out substantially flush with the outer reaches of the bumper, permitting surface treatment to be performed right up to the base of walls or other cornertype obstructions. The tapering of the edge portions 55 also permits the mouth of the opening between the housing and the surface-dressing member to be positioned close to the work surface which, together with the fact that the passageway between said housing and dressing member is angled upwardly from said work surface, permits the flow of air to sweep close to the work surface as it passes up the passageway into the housing. The sweep will bring with it a greater volume of dust and starting practically at the moment the dust is released from the work surface by the surface-dressing member. A cleaner, more effective work cleaning device results from this angled passageway commencing close to the work surface structure.

From the above description it will be apparent that a surface-dressing machine or sander is provided which is capable of providing an improved, externally operated means for converting reciprocating motion of the base plate to orbital motion or the reverse while the machine is in operation. The machine also has novel means for balancing the forces of the driving system for the surface-dressing member and includes improved self contained work surface decontamination means. An improved clamping means and guiding means are described for the strip of material or sandpaper including externally actuated release means and locking means whereby the clamp means may be released and held in released position. The base plate of the surface-dressing machine is made in a particular way and of a particular material to permit flush sanding with the machine under wet or dry conditions and said base plate is driven with a novel means that allows misalignment of the surface-dressing member relative to the driving system without damaging effects on the connection between said surface-dressing member and said driving system.

It is to be understood that the present invention is not limited to any specific construction, arrangement or form of the cooperating parts, since it is capable of numerous modifications and changes without departing from the spirit of the claims.

We claim:

1. In a surfacedressing machine having a housing, a surface-dressing member resiliently attached to said housing, said surface-dressing member having peripheral edge portions spaced from adjacent edge portions of said housing, a pair of guide means fastened to the back of said surface-dressing member, each guide means having an unattached end portion extending outwardly and away from an edge portion of said surface-dressing member and into engagement with the adjacent edge portion of the housing whereby the opposite ends of a strip of material can be guided into position between the guide means and the opposite end portions of the surface-dressing member, clamp means carried by said surface-dressing member for each of said guide means, said clamp means being urged into engagement with said guide means for urging said unattached end portions of the guide means into position against the back of said surface-dressing member for locking end portions of said strip of material to the surface-dressing member, and means carried by the housing for releasing each of said clamp means, each said release means comprising a body portion extending through an opening in said housing, a spring member in the housing urging said body portion against said housing, said body portion having an exposed portion outside the housing and having a clamp engaging portion inside the housing in close proximity to a release bar of said clamp means, and an olfset shoulder on said housing inwardly disposed from the opening in said housing, whereby inward movement of the release means contacts the clamp engaging portion with the release bar of the clamp means for moving the clamp means to released position, the body portion of said release means being urged into engagement with said offset shoulder on the housing for holding the clamp means in the released position, and movement of release means disengages the body portion from the offset shoulder to move the release means to the inactive position thereby permitting the clamp means to clamp the strip of material to the surface-dressing member.

2. In a surface-dressing machine having a housing, a surface-dressing member carried by said housing, a driving means for imparting motion to said surface-dressing member, a pair of pivotally mounted clamps supported on the back of said surface-dressing member on opposite end portions thereof, a grip portion on each clamp being urged into engagement with said back of said surface-dressing member, releasing means carired by said housing for each clamp, said releasing means comprising a body portion having a portion exposed on the outside of said housing and having a clamp engaging portion disposed within the housing in spaced relation to one end portion of the clamp to permit said clamp and surfacedressing member to move without interference from said releasing means, a stop on said housing, an edge on said body portion of the releasing means adapted to engage with said stop and spring means urging said releasing means outwardly of said housing, movement of said releasing means inwardly will engage the clamp engaging portion with the clamp to pivot the clamp to remove the grip portion from the surface-dressing member, said edge of said releasing means engaging the stop on the housing to hold the clamp in the released position, disengagement of said edge from said stop will move the releasing means into inoperative position and will permit the grip portion of the clamp to re-engage the back of said surface-dressing member.

3. In a surface-dressing machine having a housing, a surface-dressing member resiliently attached to said hous ing, a driving mechanism for imparting motion to said surface-dressing member, clamp means carried by the back portion of said surface-dressing member and having a portion urged into engagement with said back of said surface-dressing member for locking an end portion of a strip of material to the surface-dressing member, and means carried by the housing for releasing said clamp means, said release means comprising a body having a portion on the outside of the housing and a clamp engaging portion on the inside of said housing, a stop on said housing, and spring means extending between said housing and said release means whereby movement of the body into the housing engages the clamp engaging portion and release the clamp means, an edge of the body engaging with the stop on the housing for locking the clamp means in the released position, and said clamp means and body being released by upward pressure on the body to disengage the edge of the body from the stop whereby said spring urges the release means into inactive position and the clamp means engages with the strip of material to lock it to the surface-dressing member.

References Cited UNITED STATES PATENTS 2,764,852 10/1956 Emmons 51-170 2,749,676 6/ 1956 Anton 51-170 2,929,177 3/1960 Sheps 51-273 1,868,507 7/1932 Roos 5l170 JAMES L. JONES, JR., Primary Examiner 

